What is sarin?

Sarin is among the most toxic and fast-acting chemical weapons. Developed by German scientists seeking new pesticides in the 1930s, the colorless and odorless chemical is manufactured from dual-use precursor chemicals—that is, commercially available chemicals that serve legitimate industrial uses. Like VX, a more toxic nerve agent, sarin (also known as GB) disrupts the nervous system. Overstimulation of glands and muscles causes the respiratory system to shut down and can induce convulsions, paralysis, and even death if an antidote is not immediately administered.

While one drop can be fatal, sarin is nonpersistent—it disperses and vaporizes quickly—meaning that large quantities may be required to inflict mass casualties. Sarin is considered a weapon of mass destruction (WMD) under international law, but its lethality is contingent on a variety of factors, including its method of dispersion (principally through munitions such as bombs or warheads) and environmental and atmospheric conditions.

Is sarin banned under international law?

Sarin, like all chemical weapons, is banned under international law. The Organization for the Prohibition of Chemical Weapons (OPCW), the implementing body of the Chemical Weapons Convention, classifies sarin under Schedule 1, a class reserved for lethal chemicals with few, if any, legitimate, civilian applications.

The indiscriminate nature of chemical weapons violates distinction, a bedrock principle of just war theory and the law of armed conflict.

A long-standing stigma has discouraged the use of chemical weapons. The scholar Richard Price said that the "chemical weapons taboo," in his phrase, is unique—and, perhaps, uniquely effective—because the self-imposed proscription, dating to the late nineteenth century, predates the technology's development. The indiscriminate nature of chemical weapons violates distinction, a bedrock principle of just war theory and the law of armed conflict that enjoins belligerents to distinguish between combatants and civilians. This potential for "catastrophic lethality against civilian populations" has contributed to the resilience of the norm in the century since World War I.

In the Hague Declaration of 1899, thirty-two states agreed to "abstain from the use of projectiles the sole object of which is the diffusion of asphyxiating or deleterious gases." The proscription was further institutionalized by the Geneva Protocol of 1925, which prohibits the use "of asphyxiating, poisonous or other gases, and of all analogous liquids, materials or devices" in war. One hundred thirty-seven countries, including Syria, in 1968, have acceded to the protocol, which some legal experts consider to be the basis of customary law applicable to internal armed conflict.

These laws made no mention of the "development, production, and stockpiling of chemical weapons as a deterrent," which signatories vigorously pursued [PDF], the late Jonathan Tucker, a noted arms control expert, observed in 2011.

Negotiations on chemical-weapons law in the 1970s and 1980s gained momentum after Iraq's widespread use of chemical weapons and with improved U.S.-Soviet relations. Talks culminated in the Chemical Weapons Convention (CWC), which entered into force in 1997. The treaty extended the ban, prohibiting the development, production, stockpiling, transfer, and use of chemical weapons, called for the elimination of existing stocks, and established an intrusive verification regime.

With Syria's accession, all but seven countries are party to the convention; Israel and Myanmar have signed but not ratified the convention, while Angola, Egypt, North Korea, and South Sudan have neither signed nor ratified it. In October 2013, shortly after OPCW inspectors embarked on dismantling the Syrian arsenal, the Norwegian Nobel Committee awarded the Hague-based group the peace prize. With a sweeping mandate and modest resources, the OPCW is perhaps "the most important international agency nobody has ever heard about," wrote CFR Senior Fellow Stewart Patrick.

Under the Rome Statute [PDF], from which the International Criminal Court draws its authority, "employing asphyxiating, poisonous or other gases, and all analogous liquids, materials or devices" is considered a war crime. Nationals of countries not party to the Rome Statute can still be prosecuted at The Hague if the UN Security Council makes a referral.

Which countries possess sarin?

The United States and Russia built up large chemical-weapons stocks during the Cold War, but most countries that have built chemical-weapons arsenals did so to acquire a "poor man's atomic bomb," seeking a deterrent akin to that of nuclear weapons without requiring the same level of technical capacity or attracting as much international scrutiny. Syrian president Assad asserted his country's right to a chemical weapons program in 2004, saying Syria would abandon its program only if Israel disarmed its presumed nuclear arsenal.

Most countries that held chemical weapons destroyed their stocks or are in the process of doing so under the CWC. The United States has destroyed 96 percent of its declared stockpile, according to the OPCW, but the Pentagon has said it may not achieve 100 percent until 2023, despite an April 2012 deadline. Russia also missed its 2012 deadline. While the Kremlin has said it will complete its work by 2015, 53 percent of its sarin stocks remain, all in weaponized form, according to the OPCW. The Nobel committee, in its 2013 Peace Prize announcement, underscored the United States' and Russia's breach of their obligations under the CWC.

With a declared 1,300-metric-ton arsenal of sarin, mustard gas, VX, and precursor chemicals, Syria amassed what is considered to be one of the world's largest stockpiles of chemical weapons with assistance from Iran, Russia, and China. Western European and American companies abetted the process, the New York Times reported, as Assad imported precursors through a network of front companies.

Syria's disarmament under the CWC was catalyzed by a September 2013 U.S.-Russian agreement that called for the destruction of Syria's chemical weapons program "on an expedited basis." A subsequent Security Council resolution authorized a joint UN-OPCW mission to oversee the dismantling of the program. Syrian authorities are responsible for transporting CW agents to the port of Latakia, where they are transferred to international control for destruction. The multinational effort involves Danish and Norwegian cargo ships and military escorts transporting the most toxic chemicals to a specially outfitted U.S. vessel, the MV Cape Ray, for destruction in international waters. The OPCW selected two firms—one American and one Finnish—to incinerate less toxic materials in commercial facilities. China and Russia have contributed to the mission's security.

The Security Council mandated that Syria's entire chemical weapons program be dismantled by June 30, 2014, but Syria has already missed two intermediate deadlines. Though it was supposed to have removed the entire chemical stockpile by February 5, it had removed only 29 percent as of early March.

The Assad regime, which claimed that two sites were inaccessible due to fighting and a convoy carrying chemicals had been fired upon, sought to negotiate later deadlines and procure additional matériel. U.S. ambassador Robert P. Mikulak told the OPCW that this request was "without merit."

"When it comes to inspecting undeclared sites or doing something more intrusive, you really need inspectors on the ground." —Gregory Koblentz, George Mason University

Syria has also resisted destroying twelve remaining chemical weapons production facilities, contravening the OPCW's demands. Under the watchdog group's agreement with Damascus, these facilities must be destroyed by mid-March, but the Assad regime has sought to convert them to conventional military structures instead.

The joint mission's task of working on an expedited schedule amid a civil war is unprecedented, says former CFR Stanton nuclear security fellow Gregory Koblentz. Technology like GPS-enabled video cameras can mitigate some of the limitations imposed by the fighting, but cannot substitute entirely for eyewitness inspections. "When it comes to inspecting undeclared sites or doing something more intrusive, you really need inspectors on the ground," says Koblentz.

The United States and OPCW have accused Syria of dragging its feet on implementing the agreement, and some policymakers say the deal has provided Assad with insurance against foreign-backed regime change. But though the Security Council resolution does not authorize the use of force to hedge against potential noncompliance, there is sufficient international consensus behind the deal. "The Russians have a very strong stake in seeing that it gets fulfilled," says Koblentz.

Libya too developed a chemical weapons arsenal and amassed sarin precursors under Muammar al-Qaddafi, though its stocks turned out to be smaller than Western intelligence had believed. While Libya acceded to the CWC in 2004, its process of disarmament was disrupted by popular uprisings in 2011. In the subsequent tumult, previously undeclared mustard-agent-filled shells were discovered, highlighting the challenges of verification.

Have countries used sarin?

Iraq is the only state to have definitively used chemical weapons since World War II. Under Saddam Hussein, Iraq twice deployed sarin: in the Iran-Iraq War (1980–88) and against its own Kurdish minority in the north. Iraq first used chemical weapons against Iranian infantry in 1983 and escalated to sarin in the last eighteen months of the war, causing tens of thousands of casualties. Hussein also used sarin against Iraq's minority Kurdish population, assaulting the northern town of Halabja in 1988. Some 3,200 to 5,000 Kurds were killed, with thousands more injured, as Iraqi planes dropped mustard gas and nerve agents as part of a broader campaign against the Kurds.

World powers did not take legal or military action after Hussein's use of chemical weapons. But the UN Security Council moved to disarm Iraq, and U.S. strikes against the country in 1998 sought to degrade Hussein's WMD arsenal. Iraqi use may also have catalyzed progress on the CWC.

In Syria, Assad is accused of attacking opposition forces and civilians with chemical weapons on multiple occasions, culminating in an August 21, 2013, attack on Ghouta, in the Damascus suburbs, which U.S. and French intelligence say killed well over one thousand people. UN chemical-weapons inspectors concluded the following month: "The environmental, chemical, and medical samples we have collected provide clear and convincing evidence that surface-to-surface rockets containing the nerve agent sarin were used."

A determination of culpability fell beyond the inspectors' mandate. While Syrian and Russian officials have suggested that rebel forces bore responsibility for the attacks, U.S. and British ambassadors to the UN said circumstantial evidence included in the report, including details about munitions, implicated the Assad regime, a finding corroborated by some NGOs on the basis of forensic evidence. Opposition forces are not known to have such missiles.

Have nonstate actors used sarin?

Chemical weapons can be an "insidious equalizer," to use Price's phrase, which can give marginal groups the ability to cause mass casualties and widespread terror. Yet there is only one documented case of a nonstate actor using sarin, in part because of the technical sophistication required to manufacture and disseminate the poison.

Aum Shinrikyo, a messianic Japanese cult, attacked the Tokyo subway with sarin during a morning rush hour in 1995. Aum members brought sarin onto five subway cars in packages made to look like lunch boxes and bottled drinks, killing twelve and wounding thousands more. Aum, which mass-produced chemical weapons, was also implicated in the Matsumoto incident a year prior, in which the group targeted judges for assassination. A breeze shifted the plume, killing seven and injuring two hundred.

Reflecting on the subway massacre, CFR Director of Studies James M. Lindsay said, "[Advances in] technology make it possible for groups and individuals to carry out the kinds of attacks that once only governments could undertake." With purer chemicals and more effective dissemination techniques, death tolls could have been far higher [PDF]; the ratio of those killed to those injured on the Tokyo subways could have been inverted, says Raymond Zilinskas, director of the Chemical and Biological Weapons Nonproliferation Program at the Monterey Institute's Center for Nonproliferation Studies.

Two U.S. soldiers were exposed to small amounts of sarin in Iraq in May 2004 when an artillery shell containing the nerve agent, rigged as an IED, exploded. The incident was isolated, leading experts to believe that, rather than being evidence of an active WMD program prior to Saddam Hussein's ouster, the shell was a "dud" left over from Iraq's pre–Gulf War arsenal.

Since the outbreak of the civil war in Syria, the prospect of chemical weapons stocks falling into the hands of al-Qaeda–affiliated rebels, or being transferred by the Assad regime to Hezbollah, has been chief among Western concerns. Zilinskas questions whether these groups have the engineering capacity to weaponize chemical weapons, however. "I could imagine them capturing conventional rockets, but then to adapt them for chemical-weapons use would be quite a difficult feat," he says.

Additional Reources

The Economist and the New York Times provide concise histories of chemical weapons use since World War I and concomitant efforts to constrain their use.

Daniel Kevles offers a history of chemical weapons, focusing on the evolution of the United States' role in stockpiling weapons, forming strategy, and shaping international law, in the New York Review of Books.

Richard Price argues that the chemical weapons taboo is "one of the great success stories" in placing restraints on the conduct of war, and the Syria case—in which both rebels and the regime have denied using chemical weapons—has reinforced rather than undermined the norm, in the Boston Globe.

CFR's Laurie Garrett argues that "the CWC needs more teeth" and calls for more stringent international agreements covering the monitoring, surveillance, and interdiction of precursor chemicals, in an op-ed for Politico.

Human Rights Watch [PDF] conducted an independent analysis of the UN report on the Ghouta attack, finding that it was carried out by government forces. This report describes HRW's methodology.

The New York Times profiles the "relatively modest and little-known" OPCW on the occasion of the Nobel Peace Prize announcement.

Patrick Radden Keefe profiled the self-taught arms expert Eliot Higgins, who blogs under the alias Brown Moses, in the New Yorker. An accompanying video demonstrates the forensic process by which he identified the rockets allegedly used in the August 2013 Ghouta attack.